Biochemical Cause of Body Ageing

Magnus Lynch wrote:
> I am sorry if this is at a level too elementary for this newsgroup.
On the contrary; in fact it suffers from a paucity of discussion of
fundamental questions such as this.
> Could somebody please
> tell me if the cause of ageing phenomena in the human body is believed
> to be some form of inbuilt 'molecular clock' (telomeres?), random
> mutations in the DNA, or some other mechanism.
Yes and no...
Biochemical changes that give rise to macroscopic phenomena of aging are
hugely diverse; some are more naturally described as a molecular clock,
others as random events, though in fact the distinction is not very well
defined (see below). These specific molecular events are mostly quite
well understood -- in isolation.
What is not understood is their relative importance. Aging speeds up as
it progresses; thus, its rate is apparently controlled by how far it has
already progressed. But we have as yet only hypotheses for the extent to
which a given type of molecular change contributes to this rate (its own
and/or that of other types). This is particularly hard to study, partly
because many of the most plausible culprits, such as telomere shortening
or mitochondrial DNA mutation, are not yet retardable. My view is that
real progress in this area will only result from development of methods
for retarding or reversing these classes of molecular damage in model
organisms (such as mice). In some cases that may not be nearly so far
off as is popularly believed.
> If there is no inbuilt clock in the body which runs from birth to death,
> how does the body know to initiate events such as puberty?
The fundamental difficulty here is statistical. If a stochastic event is
happening often enough, it looks like a clock because the number of events
in a given time period doesn't vary very much.
Aubrey de Grey